Absorption refrigeration



' refrigerating apparatus.

Patented June 14, 1938 ABSORPTION REFRIGERATION Burgess H. Jennings,Bethlehem, Pa., assignor to The Philadelphia, and Reading Coal and IronCompany, Philadelphia, Pa., a corporation of Pennsylvania No Drawing.Application April 20, 1937,

Serial No. 137,929

9 Claims.

Ihis invention relates to absorption refrigeration, and is particularlyconcerned with solvent material for refrigerants in absorption typerefrigerating apparatus.

As is known to those acquainted with the art of absorption refrigerationa solvent material is used to absorb a refrigerant vapor in one phase ofoperation of the machine, while in another phase the refrigerant isdriven off from the solvent material because of heat supplied to thesolvent mixture. The refrigerant driven off is condensed to liquid, andby suitable means may accomplish refrigeration when it subsequentlyvaporizes. The refrigerant vapor is then again absorbed by the solventand the cycle repeats itself. In the two-fluid type of machine,mechanical means is required to circulate the refrigerant against thedifferent pressures of thesystem, and only the refrigerant and its vaporand the solvent, with very small quantities of the vapor of the latter,are present in the machine. In the three-fiuid type of machine an inertgas, which is always gas, is also present and is used to keep thepressure throughout the machine essentially constant. The inert gas isnot essentially soluble in the refrigerant or solvent of the machine.

The operation of two-fluid and three-fluid absorption refrigerationapparatus is well known to those skilled in the art, so that no detaileddescription of such apparatus need here be given. It may be brieflynoted that such apparatus comprises a generator or still in which thesolvent mixture is heated and the refrigerant driven off as a vapor, acondenser in which the refrigerant vapor is condensed to a liquid state,an evaporator in which the refrigerant liquid is vaporized at reducedpressure, and extracts heat from the medium which is to be cooled, andan absorber in which the refrigerant vapor containing, heat withdrawnfrom the refrigerated medium is again dissolved in the solvent.

A refrigerant solvent must meet satisfactorily widely varying specialconditions in absorption In the first place, in the generator or still,temperatures of from 200 to 270 F. are commonly employed. Thecharacteristics of the solvent should be such that in this temperaturerange the refrigerant in solution can, to a great extent, be removed andpass off as a gas into the condensing part of the unit. Condenser andgenerator pressures are essential- 1y equivalent. Furthermore, thesolvent in the absorber of the unit should be capable of absorbing anappreciable quantity of the refrigerant at customary absorbertemperatures of from F. to about 110 F. The absorber pressure isessentially equivalent to that of the refrigerant evaporator, whichoperates at'temperatures that may vary over a wide range but arecustomarily 5 between 0 F. and 50 F.

It will be seen from the foregoing discussion that the solvent must beable to fulfill-its functions under varying temperatures and pressures.

In addition, its freezing point should preferably 0 not be over about 10F. It should have a viscosity preferably not substantially higher than10 centipoises at 68 F. It must also be chemically stable attemperatures below 270 F., par

ticularly in regard to the common metals used 15 in refrigerationmachine construction. It must not form permanent chemical compounds withthe refrigerants used. Its specific heat should be low for the greatestefficiency. It should be capable of absorbing refrigerant at F. absorbertemperature and at the evaporator pressure maintained, and should becapable of losing at 230 F. and at the condenser pressure maintained,enough refrigerant to allow each pound of absorbent circulated areasonable car- 25 rying capacity. Its minimum boiling temperatureshould be about 240 (preferably above 260 F.) at atmospheric pressure.

I have discovered that tetrahydronaphthalene (also known as tetralin)effectively meets the requirements of a solvent in absorptionrefrigeration. Particularly I have found that this substance is adesirable solvent for the refrigerant methyl chloride under theconditions prevailing in absorption type refrigerating systems. In ad-5' peratures not greatly in excess of F. The

critical temperature value should usually not be lower than F.vaporization must be readily I possible at the pressures for which thesystem is 50 designed at temperatures as low as 0 for conventionalrefrigeration, and usually somewhat below 50 F. for air conditioningwork.

It may be noted in passing that many refrigerants are in the vacuumregion during evaporation and in some of them even during condensation,but that many others may operate in both regions or altogether in thepositive pressure region. The atmospheric boiling point of a substanceis thus not necessarily an index of its suitability as a refrigerantbecause of the possibility of operating in the vacuum region.

However, atmospheric boiling points above 120 F. do not usuallyrepresent good refrigerants.

The chemical tetrahydronaphthalene to which I refer has the empiricalformula C1oH12, consisting structurally of two'carbon rings constitutingnaphthalene, one of the rings being completely hydrogenated (except forthe double bond common to the two rings), and the other ring unchanged.This structural formula may be illustrated as follows:

The chemical is a rather stable liquid, boiling at about 206 C. andfreezing at about 25 C. It is practically non-toxic.

My invention also includes decahydronaphthalene (known also as decalin)which is suitable and satisfactory as a solvent for-absorptionrefrigeration. This chemical, the boiling point of which is about C. andthe melting point about 10 C., has the empirical formula CmCia, andstructurally consists of two carbon rings constituting naphthalene bothof which are completely hydrogenated. This formula may be illustrated asfollows:

o-o I /m in\ I claim:

1. A refrigerant mixture for absorption refrigerators, said mixturecomprising a hydrogenated naphthalene as a solvent and a volatilechemically stable refrigerant soluble in said solvent.

2. A refrigerant mixture for absorption refrigeratprs, said mixturecomprising a hydrogenated naphthalene as a solvent and a volatile.chemically-stable, halogenated .hydrocarbon refrigerant soluble in saidsolvent.

3. A refrigerant mixture for absorption refrigerators, said mixturecomprising a hydrogenated naphthalene having at least two double bondsreplaced by hydrogen atoms as asolvent and a volatile chemically stablehalogenated hydrocarbon refrigerant soluble in said solvent.

4. A refrigerant mixture for absorption refrigerators, said mixturecomprising tetrahydronaphthalene as a solvent and a volatile chemicallystable refrigerant soluble in said solvent.

5. A refrigerant mixture for absorption refrigerators, said mixturecomprising decahyd'ronaphthalene as a solvent and a volatile chemicallystable refrigerant soluble in said solvent.

6. A refrigerant mixture for absorption refrigerators, said mixturecomprising methyl chloride as the refrigerant and a hydrogenatednaphthalene as'the refrigerant solvent.

7. A-refrigerant mixture for absorption refrigerators, comprising ahydrogenated naphthalene as a solvent and a volatile, chemicallystable,halogenated aliphatic hydrocarbon refrigerant soluble in said solvent.

8. A refrigerant mixture for absorption refrigerators, comprising ahydrogenated naphthalene as a solvent and a volatile, chemically-'stable, halogenated hydrocarbon'refrigerant having not more than twocarbon atoms soluble in said solvent.

9. A refrigerant mixture for absorption refrigerators, comprising ahydrogenated naphthalene as a solvent and a volatile, chemicallystable,halogenated methane refrigerant solub in said solvent.

' BURGESS H. JENNINGS.

